High integrity SiO ₂ gate insulator formed by microwave-excited plasma enhanced chemical vapor deposition for algan/gan hybrid metal-oxide-semiconductor heterojunction field-effect transistor on si substrate

High quality SiO ₂ gate insulator has been demonstrated for GaN metal-oxide-semiconductor (MOS) transistor which has high performance with normally-off operation. The SiO ₂ films formed on GaN by microwave-excited plasma enhanced chemical vapor deposition (MW-PECVD) and annealed after deposition exhibits a low-interface state density between SiO ₂ and GaN, a high-breakdown field, and a high charge-to-breakdown. The SiO ₂ films have been also applied to the gate insulator of AlGaN/GaN hybrid MOS heterojunction field-effect transistor (HFET) on Si substrate. The MOS-HFET show excellent properties with the threshold voltage of 4.2 V and the maximum field-effect mobility of 161 cm ² V ^-1 s ^-1.